1611403721 has 2 divisors, whose sum is σ = 1611403722. Its totient is φ = 1611403720.

The previous prime is 1611403681. The next prime is 1611403733. The reversal of 1611403721 is 1273041161.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1188525625 + 422878096 = 34475^2 + 20564^2 .

It is a cyclic number.

It is not a de Polignac number, because 1611403721 - 2⁶ = 1611403657 is a prime.

It is not a weakly prime, because it can be changed into another prime (1611403741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 805701860 + 805701861.

It is an arithmetic number, because the mean of its divisors is an integer number (805701861).

Almost surely, 2^1611403721 is an apocalyptic number.

It is an amenable number.

1611403721 is a deficient number, since it is larger than the sum of its proper divisors (1).

1611403721 is an equidigital number, since it uses as much as digits as its factorization.

1611403721 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1008, while the sum is 26.

The square root of 1611403721 is about 40142.2934197836. The cubic root of 1611403721 is about 1172.3792432195.

Adding to 1611403721 its reverse (1273041161), we get a palindrome (2884444882).

The spelling of 1611403721 in words is "one billion, six hundred eleven million, four hundred three thousand, seven hundred twenty-one".